Integration of a CRISPR Cas12a-assisted multicolor biosensor and a micropipette tip enables visible point-of-care testing of foodborne Vibrio vulnificus.

Foodborne pathogens cause numerous food safety problems, and as a virulent bacterium falling under this category, Vibrio vulnificus (V. vulnificus) poses a huge threat to public health. The conventional methods used for the detection of V. vulnificus, including culture-based and molecular detection methods, have a variety of drawbacks, including being time-consuming and labor-intensive, the requirement of large-scale equipment, and the lack of professional operators. This paper establishes a visible detection platform for V. vulnificus based on CRISPR/Cas12a, which is integrated with nucleic acid isothermal amplification and ß-galactosidase-catalyzed visible color reaction. The specific vvhA gene and a conservative segment in the 16S rDNA gene of the Vibrio genus were selected as the detection targets. By using spectrum analysis, this CRISPR detection platform achieved sensitive detection of V. vulnificus (1 CFU per reaction) with high specificity. Through the color transformation system, as low as 1 CFU per reaction of V. vulnificus in both bacterial solution and artificially contaminated seafood could be visibly observed with the naked eye. Furthermore, the consistency between our assay and the qPCR assay in the detection of V. vulnificus spiked seafood was confirmed. In general, this visible detection platform is user-friendly, accurate, portable, and equipment-free, and is expected to provide a powerful supplement in point-of-care testing of V. vulnificus and also holds good promise for future application in foodborne pathogen detection.

Metabolic engineering of Lactococcus lactis for high level accumulation of glutathione and S-adenosyl-L-methionine.

Glutathione (GSH) and S-adenosyl methionine (SAM) have been applied as liver-protective factors to prevent and treat many different liver damages and diseases. Due to their low stability and short half-life, oral administration of GSH or SAM might be replaced by continuous supplying through living lactic bacteria in yogurt. In this study, Lactococcus lactis was engineered via synthetic biology strategies to produce these two important molecules. The bi-functional GSH synthase gene (gshF) and SAM synthase gene (metK) were transformed into food-grade L. lactis together with an adhesion factor gene (cwaA). The highest accumulation of SAM (9.0 mg/L) and GSH (17.3 mg/L) was achieved after 17 h cultivation of the recombinant L. lactis. Meanwhile, the autoaggregation and hydrophobicity were also improved significantly, which suggested that this engineered L. lactis might have an increased colonization-prone ability in human GI. Our studies demonstrated one potential route to self-produce and deliver the liver-healthy factors within living probiotic bacteria.

Comparison of immunogenicity and persistence between inactivated hepatitis A vaccine Healive® and Havrix® among children: A 5-year follow-up study.

BACKGROUND: Inactivated vaccines for hepatitis A virus (HAV) infection are widely used in China. Mass vaccination programs drive the need for data on long-term persistence of vaccine-induced protection. METHODS: A prospective, randomized, open-label clinical trial was conducted to compare geometric mean concentrations (GMCs) and seroconversion rates (SRs) of anti-HAV antibody elicited by the inactivated vaccines Healive and Havrix for 5 y post immunization, in which 400 healthy children were randomly assigned in a 3:1 ratio to receive 2 doses of Healive or Havrix at 0 and 6 month. Anti-HAV antibody concentration was detected by microparticle enzyme immunoassay (MEIA) during the study. Furthermore, an attempt was made to predict persistence of protective immunogenicity by using a suitable statistical model. RESULTS: The GMCs were significantly higher after vaccination with Healive than after Havrix as comparator vaccine at 1, 6, 7, 18, 30, 42, 54 and 66 month (P < 0.01) with the peak point at 7 month (3427.2 mIU/ml for Healive and 1441.9 mIU/ml for Comparator). Similarly significant differences of SRs were found between the 2 groups at 1 and 6 month (P < 0.01). Afterwards, the SRs of both groups reached 100% at 7 month and did not decline until 66 month(99.1% for Healive and 97.5% for Comparator). A linear mixed model with a change point at 18 month(Model 3) was found to be suitable to predict persistence of protective immunogenicity induced by vaccines. It was estimated that the duration of protection for Healive was at least 20 y with a lower limit of GMC 95% confidence interval (CI) no less than 20 mIU/mL. CONCLUSIONS: Compared with Havrix, the new preservative-free inactivated hepatitis A vaccine (Healive) in 2 doses showed better persistence of antibody concentrations for 5 y after full-course immunization among children and the persistence of protective immunogenicity was estimated for at least 20 y.